New Aspects of Carrier Multiplication in Semiconductor Nanocrystals

We investigate carrier multiplication in PbSe NCs by applying time-resolved photoluminescence and transient absorption

John A. McGuire; Jin Joo; Jeffrey M. Pietryga; Richard D. Schaller; Victor I. Klimov

2008

Scholarcy highlights

  • One consequence of strong spatial confinement of electronic wave functions in semiconductor nanocrystals is a significant enhancement in carrier−carrier Coulomb interactions
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  • This effect leads to a number of novel physical phenomena including ultrafast decay of multiple electron−hole pairs by Auger recombination and high-efficiency generation of mutiexcitons by single photons via carrier multiplication
  • Because of restrictions imposed by energy and translational-momentum conservation, as well as rapid energy loss due to phonon emission, CM is inefficient in bulk semiconductors, at energies relevant to solar energy conversion
  • The CM efficiency can potentially be enhanced in zero-dimensional NCs because of factors such as a wide separation between discrete electronic states, which inhibits phonon emission, enhanced Coulomb interactions, and relaxation in translational-momentum conservation
  • NCs of the same energy gap show moderate batch-to-batch variations in apparent multiexciton yields and larger variations due to differences in sample conditions. These results indicate that NC surface properties may affect the CM process
  • Further optimization of carrier multiplication performance should be possible by utilizing more complex NCs that allow for facile manipulation of carrier−carrier interactions, as well as single and multiexciton energies and dynamics

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